Method and apparatus for treating sleep apnea

ABSTRACT

An oral appliance is disclosed that provides electrical stimulation to a patient&#39;s tongue in a manner that prevents collapse of the tongue and/or soft palate during sleep. More specifically, the appliance may induce a reversible current or currents in a lateral direction across the tongue in a manner that shortens the patient&#39;s Palatoglossus muscle, which in turn pulls the patient&#39;s soft palate downward towards a base of the tongue and/or decreases a volume of the tongue.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application, and claims the benefit ofco-pending and commonly owned U.S. patent application Ser. No.14/149,689 entitled “METHOD AND APPARATUS FOR TREATING SLEEP APNEA”filed on Jan. 7, 2014, which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

The present embodiments relate generally to sleep apnea, andspecifically to non-invasive techniques for treating one or moreunderlying causes and results of sleep apnea.

BACKGROUND OF RELATED ART

Obstructive sleep apnea (OSA) is a medical condition in which apatient's upper airway is repeatedly partially or fully occluded duringsleep. These repeated occlusions of the upper airway may cause sleepfragmentation, which in turn may result in sleep deprivation, daytimetiredness, and malaise. More serious instances of OSA may increase thepatient's risk for stroke, cardiac arrhythmias, high blood pressure,and/or other disorders.

OSA may be characterized by the tendency of the soft tissues of theupper airway to collapse during sleep, thereby occluding the upperairway. More specifically, OSA is typically caused by the collapse ofthe patient's soft palate and/or by the collapse of the patient's tongue(e.g., onto the back of the pharynx), which in turn may obstruct normalbreathing.

There are many treatments available for OSA including, for example:surgery, constant positive airway pressure (CPAP) machines, and theelectrical stimulation of muscles associated with moving the tongue.Surgical techniques include tracheotomies, procedures to remove portionsof a patient's tongue and/or soft palate, and other procedures that seekto prevent collapse of the tongue into the back of the pharynx. Thesesurgical techniques are very invasive. CPAP machines seek to maintainupper airway patency by applying positive air pressure at the patient'snose and mouth. However, these machines are uncomfortable and may havelow compliance rates.

Some electrical stimulation techniques seek to prevent collapse of thetongue into the back of the pharynx by causing the tongue to protrudeforward (e.g., in an anterior direction) during sleep. For one example,U.S. Pat. No. 4,830,008 to Meer discloses an invasive technique in whichelectrodes are implanted into a patient at locations on or near nervesthat stimulate the Genioglossus muscle to move the tongue forward (e.g.,away from the back of the pharynx). For another example, U.S. Pat. No.7,711,438 to Lattner discloses a non-invasive technique in whichelectrodes, mounted on an intraoral device, electrically stimulate theGenioglossus muscle to cause the tongue to move forward duringrespiratory inspiration. In addition, U.S. Pat. No. 8,359,108 toMcCreery teaches an intraoral device that applies electrical stimulationto the Hypoglossal nerve to contract the Genioglossus muscle, which asmentioned above may prevent tongue collapse by moving the tongue forwardduring sleep.

Moving a patient's tongue forward during sleep may cause the patient towake, which is not desirable. In addition, existing techniques forelectrically stimulating the Hypoglossal nerve and/or the Genioglossusmuscle may cause discomfort and/or pain, which is not desirable.Further, invasive techniques for electrically stimulating theHypoglossal nerve and/or the Genioglossus muscle undesirably requiresurgery and introduce foreign matter into the patient's tissue, which isundesirable.

Thus, there is a need for a non-invasive treatment for OSA that does notdisturb or wake-up the patient during use.

SUMMARY

This Summary is provided to introduce in a simplified form a selectionof concepts that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tolimit the scope of the claimed subject matter.

A method and apparatus for reducing the occurrence and/or severity of abreathing disorder, such as OSA, are disclosed herein. In accordancewith the present embodiments, a non-invasive and removable oralappliance is disclosed that may provide electrical stimulation to alateral and/or sublingual portion of a patient's oral cavity (mouth) ina manner that prevents a collapse of the patient's tongue and/or softpalate during sleep without disturbing (e.g., without waking) thepatient. For at least some embodiments, an electric current induced bythe appliance may stimulate the patient's Palatoglossus muscle in amanner that causes the Palatoglossus muscle to stiffen and shorten,which in turn may pull the patient's soft palate and/or palatal archesin a downward direction towards a base of the patient's tongue so as toprevent the soft palate from collapsing and/or from flapping against theback of the patient's throat. Stiffening and/or shortening thePalatoglossus muscle may also cause the patient's tongue to contractand/or stiffen in a manner that prevents collapse of the tongue in aposterior direction (e.g., towards the patient's pharynx).

In addition, stimulating the Palatoglossus muscle using techniquesdescribed herein may also lower a superior surface of the tongue T,thereby causing the tongue to cinch downward (e.g., to “hunker down”) ina manner that further prevents obstruction of the patient's upperairway. By simultaneously preventing collapse of the patient's softpalate and tongue, patency of the patient's upper airway may bemaintained in a non-invasive manner. For some embodiments, the appliancemay stimulate the patient's Palatoglossus muscle without moving thepatient's tongue in an anterior direction. For at least one embodiment,stimulation of the patient's Palatoglossus muscle may also elevate aposterior portion of the patient's tongue, which in turn may furtherprevent collapse of the tongue onto the back of the patient's pharynx.

BRIEF DESCRIPTION OF THE DRAWINGS

The present embodiments are illustrated by way of example and are notintended to be limited by the figures of the accompanying drawings,where like reference numerals refer to corresponding parts throughoutthe drawing figures.

FIG. 1A is a side sectional view depicting a patient's upper airway.

FIG. 1B is a front plan view of the patient's oral cavity.

FIG. 1C is an elevated sectional view of the patient's tongue.

FIG. 1D is a side sectional view of the patient's tongue.

FIG. 2A is a top plan view of a device, situated over a patient's lowerteeth, in accordance with some embodiments.

FIG. 2B is an elevated perspective view of the device of FIG. 2A.

FIG. 2C is a top plan view of a device, situated over a patient's lowerteeth, in accordance with other embodiments.

FIG. 2D is an elevated perspective view of the device of FIG. 2C.

FIG. 3A is a side sectional view depicting a patient's upper airwayduring disturbed breathing.

FIG. 3B is a side sectional view depicting the patient's upper airway inresponse to electrical stimulation provided in accordance with theexample embodiments.

FIG. 4 is a block diagram of the electrical components of the device ofFIGS. 2A-2B.

FIG. 5 is a circuit diagram illustrating an electrical model of thepatient's tongue.

FIG. 6 is an illustrative flow chart depicting an example operation inaccordance with some embodiments.

FIG. 7A is an elevated perspective view of a device in accordance withother embodiments.

FIG. 7B is an elevated perspective view of the device of FIG. 7Asituated over a patient's teeth.

FIG. 7C is a rear plan view of the device of FIG. 7A situated over apatient's teeth.

FIG. 7D is a front plan view of the device of FIG. 7A situated over apatient's teeth.

DETAILED DESCRIPTION

A non-invasive method and apparatus for treating sleep disorders, suchas obstructive sleep apnea (OSA) and/or snoring, are disclosed herein.In the following description, numerous specific details are set forth toprovide a thorough understanding of the present disclosure. Also, in thefollowing description and for purposes of explanation, specificnomenclature is set forth to provide a thorough understanding of thepresent embodiments. However, it will be apparent to one skilled in theart that these specific details may not be required to practice thepresent embodiments. In other instances, well-known circuits and devicesare shown in block diagram form to avoid obscuring the presentdisclosure. The term “coupled” as used herein means connected directlyto or connected through one or more intervening components, circuits, orphysiological matter. Any of the signals provided over various busesdescribed herein may be time-multiplexed with other signals and providedover one or more common buses, or may be wirelessly transmitted betweena number of component, circuits, sensors, and/or devices of the exampleembodiments. Additionally, the interconnection between circuit elementsor software blocks may be shown as buses or as single signal lines. Eachof the buses may alternatively be a single signal line, and each of thesingle signal lines may alternatively be buses, and a single line or busmight represent any one or more of a myriad of physical or logicalmechanisms for communication between components. Further, the logiclevels and timing assigned to various signals in the description beloware arbitrary and/or approximate, and therefore may be modified (e.g.,polarity reversed, timing modified, etc) as desired.

As used herein, the term “substantially lateral direction” refers to adirection across the patient's oral cavity in which the direction'slateral components are larger than the direction's anterior-to-posteriorcomponents (e.g., a substantially lateral direction may refer to anydirection that is less than approximately 45 degrees from the lateraldirection, as defined below with respect to the drawing figures).Further, as used herein, the term “reversible current” means a currentthat changes or reverses polarity from time to time between twocontrollable voltage potentials.

To more fully understand the present embodiments, the dynamics of OSAare first described with respect to an illustration 100 of a patient'soral cavity shown in FIGS. 1A-1D, which illustrate the anatomicalelements of a patient's upper airway (e.g., including the nasal cavity,oral cavity, and pharynx of the patient). Referring first to FIGS.1A-1B, the hard palate HP overlies the tongue T and forms the roof ofthe oral cavity OC (e.g., the mouth). The hard palate HP includes bonesupport BS, and thus does not typically deform during breathing. Thesoft palate SP, which is made of soft material such as membranes,fibrous material, fatty tissue, and muscle tissue, extends rearward(e.g., in a posterior direction) from the hard palate HP towards theback of the pharynx PHR. More specifically, an anterior end 1 of thesoft palate SP is anchored to a posterior end of the hard palate HP, anda posterior end 2 of the soft palate SP is un-attached. Because the softpalate SP does not contain bone or hard cartilage, the soft palate SP isflexible and may collapse onto the back of the pharynx PHR and/or flapback and forth (e.g., especially during sleep).

The pharynx PHR, which passes air from the oral cavity OC and nasalcavity NC into the trachea TR, is the part of the throat situatedinferior to (below) the nasal cavity NC, posterior to (behind) the oralcavity OC, and superior to (above) the esophagus ES. The pharynx PHR isseparated from the oral cavity OC by the Palatoglossal arch PGA, whichruns downward on either side to the base of the tongue T.

Although not shown for simplicity, the pharynx PHR includes thenasopharynx, the oropharynx, and the laryngopharynx. The nasopharynxlies between an upper surface of the soft palate SP and the wall of thethroat (i.e., superior to the oral cavity OC). The oropharynx liesbehind the oral cavity OC, and extends from the uvula U to the level ofthe hyoid bone HB. The oropharynx opens anteriorly into the oral cavityOC. The lateral wall of the oropharynx consists of the palatine tonsil,and lies between the Palatoglossal arch PGA and the Palatopharyngealarch. The anterior wall of the oropharynx consists of the base of thetongue T and the epiglottic vallecula. The superior wall of theoropharynx consists of the inferior surface of the soft palate SP andthe uvula U. Because both food and air pass through the pharynx PHR, aflap of connective tissue called the epiglottis EP closes over theglottis (not shown for simplicity) when food is swallowed to preventaspiration. The laryngopharynx is the part of the throat that connectsto the esophagus ES, and lies inferior to the epiglottis EP.

Referring also to FIGS. 1C-1D, the tongue T includes a plurality ofmuscles that may be classified as either intrinsic muscles or extrinsicmuscles. The intrinsic muscles, which lie entirely within the tongue Tand are responsible for altering the shape of the tongue T (e.g., fortalking and swallowing), include the superior longitudinal muscle SLM,the inferior longitudinal muscle ILM, the vertical muscle VM, and thetransverse muscle TM. The superior longitudinal muscle SLM runs alongthe superior surface SS of the tongue T under the mucous membrane, andmay be used to elevate, retract, and deviate the tip of the tongue T.The inferior longitudinal muscle ILM lines the sides of the tongue T,and is attached to the Styloglossus muscle SGM. The vertical muscle VMis located along the midline of the tongue T, and connects the superiorand inferior longitudinal muscles together. The transverse muscle TMdivides the tongue at the middle, and is attached to the mucousmembranes that run along the sides of the tongue T.

The extrinsic muscles, which attach the tongue T to other structures andare responsible for re-positioning (e.g., moving) the tongue, includethe Genioglossus muscle GGM, the Hyoglossus muscle HGM, the Styloglossusmuscle SGM, and the Palatoglossus muscle PGM. The Genioglossus muscleGGM may be used to protrude the tongue T and to depress the center ofthe tongue T. The Hyoglossus muscle HGM may be used to depress thetongue T. The Styloglossus muscle SGM may be used to elevate and retractthe tongue T. The Palatoglossus muscle PGM may be used to depress thesoft palate SP and/or to elevate the back (posterior portion) of thetongue T. Referring also to FIGS. 1A and 1B, the Palatoglossus musclePGM connects the tongue T to both sides of the Palatoglossus arch PGA,and inserts into lateral posterior regions 101 of the base of the tongueT.

It is noted that all of the muscles of the tongue T, except for thePalatoglossus muscle PGM, are innervated by the Hypoglossal nerve (notshown for simplicity); the Palatoglossus muscle PGM is innervated by thepharyngeal branch of the Vagus nerve (not shown for simplicity).

During awake periods, the muscles of the upper airway (as well as thehypoglossal nerve) are active and stimulated, and may maintain upperairway patency by preventing the soft palate SP from collapsing and/orby preventing the tongue T from prolapsing onto the back of the pharynxPHR. However, during sleep periods, a relative relaxed state of the softpalate SP may allow the soft palate SP to collapse and obstruct normalbreathing, while a relative relaxed state of the tongue T may allow thetongue T to move in a posterior direction (e.g., onto the back of thepharynx PHR) and obstruct normal breathing.

Accordingly, conventional electrostimulation treatments for OSAtypically involve causing the tongue T to move forward in the anteriordirection during apnea episodes so that the tongue T does not collapsein the posterior direction. More specifically, some conventionaltechniques (e.g., disclosed in U.S. Pat. Nos. 5,190,053 and 6,212,435)electrically stimulate the Genioglossus muscle to move the tongueforward in an anterior direction during apnea episodes, while otherconventional techniques (e.g., disclosed in U.S. Pat. No. 8,359,108)electrically stimulate the Hypoglossal nerve, which in turn causes thetongue to move forward in the anterior direction by innervating theGenioglossus muscle.

Unfortunately, repeatedly moving the tongue T forward (e.g., in theanterior direction) to prevent its prolapse into the back of the pharynxPHR may undesirably wake-up the patient, which defeats the very purposeof OSA treatments and may also abrade the tongue on the teeth. Indeed,electrically stimulating the relatively large Genioglossus muscle maycause discomfort or pain. In addition, because the Hypoglossal nerveinnervates every tongue muscle except the Palatoglossus muscle PGM,electrically stimulating the Hypoglossal nerve may stimulate not onlythe Genioglossus muscle GGM but also the superior longitudinal muscleSLM, the inferior longitudinal muscle ILM, the vertical muscle VM, thetransverse muscle TM, the Hyoglossus muscle HPM, and/or the Styloglossusmuscle SSM. Stimulating multiple tongue muscles at the same time, in anattempt to move the tongue forward during apnea episodes, may not onlyover-stimulate the patient's tongue muscles but may also cause thetongue T to behave erratically (e.g., repeatedly protruding andretracting). For example, simultaneously stimulating the Genioglossusmuscle GGM and the Styloglossus muscle SGM may cause the tongue T torepeatedly protrude and retract, respectively, which is likely todisturb the patient's sleep patterns or even wake-up the patient.

Applicant has discovered that OSA may be more effectively treated bytargeting the Palatoglossus muscle PGM for electrical stimulation (e.g.,rather than targeting the Genioglossus muscle GGM or the Hypoglossalnerve for electrical stimulation). More specifically, Applicant hasdiscovered that application of one or more voltage differentials acrossselected portions of the patient's lateral or sublingual tissue mayinduce a current across the tongue to electrically stimulate thePalatoglossus muscle PGM in a manner that causes the Palatoglossusmuscle PGM to shorten (e.g., to decrease its length). For at least someembodiments, the induced current may flow in a lateral direction acrossa base portion of the patient's tongue (e.g., proximate to the lateralpoints at which the Palatoglossus muscle inserts into the tongue T).Shortening the Palatoglossus muscle, using techniques described herein,may (1) stiffen and reduce the volume of the tongue T and (2) may causethe Palatoglossal arch PGA to pull down (e.g., in a downward direction)towards the base of the tongue T.

As described in more detail below, reducing the volume of the tongue Tusing techniques described herein may prevent the tongue T fromprolapsing onto the back of the pharynx PHR, and pulling down thePalatoglossal arch PGA using techniques described herein may prevent thesoft palate SP from collapsing onto the back of the pharynx PHR. Inaddition, stimulating the Palatoglossus muscle PGM using techniquesdescribed herein may also lower the superior surface SS of the tongue T,thereby causing the tongue to cinch downward (e.g., to “hunker down”) ina manner that further prevents obstruction of the patient's upperairway.

Perhaps equally important, because the present embodiments do not targeteither the Hypoglossal nerve or the Genioglossus muscle GGM forelectrical stimulation, the present embodiments may not cause the tongueT to move forward in the anterior direction during application of theelectrical stimulation, which in turn may reduce the likelihood ofundesirably waking-up the patient. Indeed, for at least someembodiments, the voltage differential may be applied across thepatient's sublingual or lateral lingual tissues in a manner thatmaintains the patient's tongue in a substantially stationary positionwhile shortening the patient's Palatoglossus muscle PGM. In this manner,the present embodiments may maintain a patient's upper airway patency ina subtle yet therapeutic manner. Although electrical stimulation of thePalatoglossus muscle PGM using techniques described herein is notintended to stimulate the Genioglossus muscle GGM, any inadvertentstimulation of the Genioglossus muscle GGM will be relatively small and,at most, may serve to maintain the tongue T in a substantiallystationary position.

FIGS. 2A-2B show a removable oral appliance 200 that, in accordance withat least some embodiments, may be used to treat OSA by using electricalstimulation of the Palatoglossus muscle PGM to prevent collapse of thetongue T and soft palate SP into the back of the pharynx PHR. Theappliance 200 is shown in FIGS. 2A-2B as including an appliance body 205upon which a number of electrodes 210(1)-210(2), a control circuit 220,and a power supply 230 may be mounted (or otherwise attached to) so asto form a unitary and removable device that may fit generally within apatient's oral cavity OC (see also FIGS. 1A-1B). For such embodiments,there are no components external to the patient's body, and thereforethe appliance 200 may not be associated with wires or other connectorsthat protrude from the patient's mouth or body. For some embodiments,the oral appliance 200 may be fitted over a patient's lower teeth andpositioned to fit within a sublingual portion of the patient's oralcavity OC, for example, as depicted in FIG. 2A. For other embodiments,appliance 200 may be of other suitable configurations or structures, andthe electrodes 210(1)-210(2) may be provided in other suitablepositions. For some embodiments, there may be a minor portion of theoral appliance that protrudes slightly outside the lips or mouth. Forother embodiments, the control circuit 220, power supply 230, and/orother components may be detached from the appliance 200 and locatedoutside the patient's mouth. For such embodiments, the control circuit220, power supply 230, and/or other components may be electricallycoupled to the electrodes 210(1)-210(1) using wired connections (e.g.,conductive wires).

Although only two electrodes 210(1)-210(1) are shown in FIGS. 2A-2B, itis to be understood that the appliance 200 may, in other embodiments,include a greater or fewer number of electrodes. For example, in otherembodiments, the appliance 200 may include four or another number ofelectrodes 210 arranged in opposing (e.g., “X”) patterns with respect tothe patient's sublingual tissues, wherein pairs of the electrodes may beselectively enabled and disabled in a manner that alternately inducestwo or more currents across the patient's sublingual tissues. For suchother embodiments, each of such electrodes may be turned on and/or offindependently of the other electrodes, for example, to determine a pair(or more) of electrodes that, at a particular moment for the patient,correlate to optimum electrical stimulation. The determined pair ofelectrodes may be dynamically selected either by (1) directlycorrelating electrical stimulation and immediate respiratory response orby (2) indirectly using the oral appliance 200 “to look for” the lowestimpedance electrode “pair(s).” The determined electrodes may or may notbe at the ends of an “X” pattern, and may be opposing one another.

The first electrode 210(1) and the second electrode 210(2), which may beformed using any suitable material and may be of any suitable sizeand/or shape, are connected to the control circuit 220 by wires 221. Thewires 221 may be any suitable wire, cable, conductor, or otherconductive element that facilitates the exchange of signals betweencontrol circuit 220 and the electrodes 210(1)-210(2). The controlcircuit 220 and electrodes 210(1)-210(2) are electrically coupled topower supply 230 via wires 221. Note that the wires 221 may bepositioned either within or on an outside surface of the appliance body205, and therefore do not protrude into or otherwise contact thepatient's tongue or oral tissue. The power supply 230 may be mounted inany of several locations and may be any suitable power supply (e.g., abattery) that provides power to control circuit 220 and/or electrodes210(1)-210(2). Bi-directional gating techniques may be used to controlvoltages and/or currents within wires 221, for example, so that wires221 may alternately deliver power to electrodes 210(1)-210(2) andexchange electrical signals (e.g., sensor signals) between electrodes240(1)-240(2) and control circuit 220.

For the example embodiment of FIGS. 2A-2B, the first electrode 210(1)may include or also function as a sensor 240(1), and the secondelectrode 210(2) may include or also function as a sensor 240(2), whichcould sense respiration or other functions of interest. In other words,for some embodiments, one or both of electrodes 210(1)-210(2) may alsofunction as sensors such as respiration sensors. For such embodiments,the active function of the electrodes 210(1)-210(2) may be controlledusing bi-directional gating techniques. For example, when the firstelectrode 210(1) is to function as a driven electrode, thebi-directional gating technique may connect the first electrode 210(1)to the output of a circuit such as a voltage and/or current driver(e.g., included within or associated with control circuit 220), forexample, to provide a first voltage potential at the first electrode210(1); conversely, when the first electrode 210(1) is to function asthe respiration sensor or other sensor 240(1), the bi-directional gatingtechnique may connect sensor 240(1) to the input of a circuit such as anamplifier and/or an ADC (analog to digital) converter (e.g., includedwithin or associated with control circuit 220), for example, to sense arespiratory function of the patient. Similarly, when the secondelectrode 210(2) is to function as a driven electrode, thebi-directional gating technique may connect the second electrode 210(2)to the output of a circuit such as a voltage and/or current driver(e.g., included within or associated with control circuit 220), forexample, to provide a second voltage potential at the second electrode210(2); conversely, when the second electrode 210(2) is to function asthe respiration sensor or other sensor 240(2), the bi-directional gatingtechnique may connect sensor 240(2) to the input of a circuit such as anamplifier and/or an ADC (analog to digital) converter (e.g., includedwithin or associated with control circuit 220), for example, to sense arespiratory function of the patient.

The respiration sensors or other sensors 240(1)-240(2), as providedwithin or otherwise associated with the electrodes 210(1)-210(2), may beany suitable sensors that measure any physical, chemical, mechanical,electrical, neurological, and/or other characteristics of the patientwhich may indicate or identify the presence and/or absence of disturbedbreathing. These respiration sensors 240(1)-240(2) may also be used todetect snoring. For at least some embodiments, one or both of electrodes210(1)-210(2) may include electromyogram (EMG) sensor electrodes that,for example, detect electrical activity of the muscles and/or nerveswithin, connected to, or otherwise associated with the oral cavity. Forat least one embodiment, one or both of electrodes 210(1)-210(2) mayinclude a microphone (or any other sensor to sense acoustic and/orvibration energy) to detect the patient's respiratory behavior. Forother embodiments, one or both of electrodes 210(1)-210(2) may includeone or more of the following non-exhaustive list of sensors:accelerometers, piezos, capacitance proximity detectors, capacitivesensing elements, optical systems, EMG sensors, etc.

For other embodiments, electrodes 210(1)-210(2) may not include anysensors. For at least one of the other embodiments, the electrodes210(1)-210(2) may continuously provide electrical stimulation to thepatient's Palatoglossus muscle PGM via the lingual tissues. For analternative embodiment, a timer (not shown for simplicity) may beprovided on appliance body 205 or within control circuit 220 andconfigured to selectively enable/disable electrodes 210(1)-210(2), forexample, based upon a predetermined stimulation schedule. In anotherclosed-loop embodiment, the electrodes 210(1)-210(2) may be selectivelyenabled/disabled based upon one or more sources of sensor feedback fromthe patient.

For the example embodiment of FIGS. 2A-2B, the first and secondelectrodes 210(1)-210(2) may be mounted on respective lateral arms205(1) and 205(2) of the body 205 of appliance 200 such that whenappliance 200 is placed within a sublingual portion of the patient'soral cavity OC, the first and second electrodes 210(1)-210(2) arepositioned on opposite sides of the posterior sublingual region 207 ofthe patient's oral cavity OC. For other embodiments, the first andsecond electrodes 210(1)-210(2) may be separate from appliance body 205but connected to respective lateral arms 205(1)-205(2), for example, soas to “float” beneath or on either side of the patient's tongue T, oralternatively oriented so as to be positioned on opposite sides of thesuperior surface of the tongue T. For some embodiments, the first andsecond electrodes 210(1)-210(2) are positioned in the posteriorsublingual region 207 of the oral cavity OC such that at least a portionof each of the first and second electrodes 210(1)-210(2) is proximal toa molar 209 of the patient. In this manner, the first and secondelectrodes 210(1)-210(2) may be in physical contact with the patient'slingual tissues proximate to the lateral posterior regions (e.g.,points) 101 at which the Palatoglossus muscle PGM inserts into thetongue T (see also FIGS. 1A-1B). Further, as depicted in FIGS. 2A-2B,the first and second electrodes 210(1)-210(2) may be angularly orientedwith respect to the floor of the mouth such that the first and secondelectrodes 210(1)-210(2) substantially face and/or contact oppositesides of the tongue T proximate to the lateral posterior regions (e.g.,points) 101 at which the Palatoglossus muscle PGM inserts into thetongue T (see also FIGS. 1A-1B). For other embodiments, the first andsecond electrodes 210(1)-210(2) may be provided in one or more otherpositions and/or orientations.

The control circuit 220 may provide one or more signals to the first andsecond electrodes 210(1)-210(2) to create a voltage differential acrossthe patient's lingual tissues (e.g., across the base of the tongue) inthe lateral direction. For purposes of discussion herein, the firstelectrode 210(1) may provide a first voltage potential V1, and thesecond electrode 210(2) may provide a second voltage potential V2. Thevoltage differential (e.g., V2-V1) provided between the first and secondelectrodes 210(1)-210(2) may induce a current 201 in a substantiallylateral direction across the patient's lingual tissues. For someembodiments, the current 201 is induced in a substantially lateraldirection across the patient's tongue. The current 201, which for someembodiments may be a reversible current (as described in more detailbelow), electrically stimulates the patient's Palatoglossus muscle PGMin a manner that shortens the Palatoglossus muscle PGM.

When the Palatoglossus muscle PGM is stimulated and/or shortened inresponse to the current 201 induced by the first and second electrodes210(1)-210(2), the Palatoglossus muscle PGM causes the tongue T tostiffen in a manner that decreases the tongue's volume, and that mayalso slightly cinch a portion of the tongue T closer to the floor of theoral cavity OC. One or more of decreasing the tongue's volume andslightly cinching the tongue T downward towards the floor of the oralcavity OC may prevent the tongue T from prolapsing onto the back of thepharynx PHR, thereby maintaining patency of the patient's upper airway(e.g., without moving the tongue forward in the anterior direction). Theshortening of the Palatoglossus muscle PGM may also pull the patient'sPalatoglossal arch PGA in a downward direction towards the base of thetongue T, which in turn may prevent the soft palate SP from collapsingand obstructing the patient's upper airway.

For example, FIG. 3A shows a side view 300A of a patient depicting thecollapse of the patient's tongue T and soft palate SP in a posteriordirection towards the back of the pharynx (PHR) during disturbedbreathing. As depicted in FIG. 3A, the patient's upper airway isobstructed by the tongue T prolapsing onto the back wall of the pharynxPHR and/or by the soft palate SP collapsing onto the back wall of thepharynx PHR.

In contrast, FIG. 3B shows a side view 300B of the patient depicting thepatient's upper airway response to electrical stimulation provided inaccordance with the present embodiments. More specifically, electricalstimulation provided by one or more embodiments of the appliance 200 maycause the Palatoglossus muscle PGM to stiffen and shorten, which in turnmay pull the patient's soft palate SP and/or palatal arches in adownward direction, thereby preventing the soft palate SP fromcollapsing onto the back wall of the pharynx PHR. In addition,stiffening and/or shortening the Palatoglossus muscle PGM may also causethe patient's tongue T to contract and/or cinch downward in a mannerthat prevents collapse of the tongue T towards the back of the pharynxPHR without substantially moving the tongue T forward in the anteriordirection.

The control circuit 220 may be any suitable circuit or device (e.g., aprocessor) that causes electrical stimulation energy to be provided toareas proximate to the base of the patient's tongue T via the electrodes210(1)-210(2). More specifically, the control circuit 220 may generateone or more voltage waveforms that, when provided as signals and/ordrive signals to the first and second electrodes 210(1)-210(2),primarily induces a current across (e.g., in a substantially lateraldirection) one or more portions of the patient's upper airway (e.g.,across a lingual portion of the patient's tongue T) in a manner thatcauses the patient's Palatoglossus muscle PGM to shorten. As usedherein, inducing a current across one or more portions of the patient'supper airway refers to a direction between left and right sides of thepatient's oral cavity. The waveforms provided by control circuit 220 mayinclude continuous voltage waveforms, a series of pulses, or acombination of both. The control circuit 220 may be formed using digitalcomponents, analog components, or a combination of analog and digitalcomponents.

For some embodiments, the control circuit 220 may vary or modify thewaveform in a manner that induces a reversible current across one ormore portions of the patient's upper airway (e.g., across a portion ofthe patient's tongue T). Applicant has discovered that inducing areversible current across one or more portions of the patient's upperairway may decrease the likelihood of patient discomfort (e.g., ascompared with providing a constant current or current in a singledirection). More specifically, Applicant notes that when a current isinduced in the lingual tissues of the patient, the lingual tissues mayexperience ion or carrier depletion, which in turn may require greatervoltage differentials and/or greater current magnitudes to maintain adesired level of electrical stimulation of the Palatoglossus muscle PGM.However, inducing greater voltage and/or current magnitudes to offsetincreasing levels of ion or carrier depletion may create patientdiscomfort. Thus, to prevent ion or carrier depletion of the patient'ssublingual tissues, the control circuit 220 may limit the duration ofpulses that induce the current 201 across the sublingual tissues and/ormay from time to time reverse the direction (e.g., polarity) of thecurrent 201 induced across the patient's sublingual tissues.

For some embodiments, control circuit 220 may generate and/ordynamically adjust the waveform and/or drive waveform provided to thefirst and second electrodes 210(1)-210(2) (and/or to a number ofadditional electrodes, not shown for simplicity) in response to one ormore input signals indicative of the patient's respiratory behaviorand/or inputs from other characteristics and sensing methods. The inputsignals may be provided by one or more of the sensors 240(1)-240(2)integrated within respective electrodes 210(1)-210(2).

For other embodiments, sensors other than the sensors 240(1)-240(2)integrated within respective electrodes 210(1)-210(2) may be used togenerate the input signals. For example, FIGS. 2C-2D show a removableoral appliance 270 in accordance with other embodiments. Appliance 270may include all the elements of the appliance 200 of FIGS. 2A-2B, plusadditional sensors 240(3)-240(4). For the example embodiment of FIGS.2C-2D, the sensor 240(3) may be an oxygen saturation (O₂ sat) sensorthat provides a signal indicative of the patient's oxygen saturationlevel, and the sensor 240(4) may be a vibration sensor that provides asignal indicative of the patient's respiratory activity (as measured byvibrations detected within the patient's oral cavity). For otherembodiments, sensors 240(3)-240(4) may be other types of sensorsincluding, for example, sensors that measure air composition (especiallyO₂ and CO₂), heart rate, respiration, temperature, head position,snoring, pH levels, and others.

FIG. 4 shows a block diagram of the electrical components of anappliance 400 that is one embodiment of the appliance 200 of FIGS.2A-2B. Appliance 400 is shown to include a processor 410, a plurality ofelectrodes 210(1)-210(n), power supply 230, sensors 240, and an optionaltransceiver 420. Processor 410, which is one embodiment of the controlcircuit 220 of FIGS. 2A-2B, includes a waveform generator 411, a memory412, and a power module 413. The power supply 230, which as mentionedabove may be any suitable power supply (e.g., a battery), provides power(PWR) to processor 410. For some embodiments, the processor 410 may usepower module 413 to selectively provide power to sensors 240, forexample, only during periods of time that the sensors 240 are to beactive (e.g., only when it is desired to receive input signals fromsensors 240). Selectively providing power to sensors 240 may not onlyreduce power consumption (thereby prolonging the battery life of powersupply 230) but may also minimize electrical signals transmitted alongwires 221 to the processor 410. For other embodiments, power supply 230may provide power directly to sensors 240.

The sensors 240, which may include sensors 240(1)-240(2) of FIGS. 2A-2Band/or sensors 240(3)-240(4) of FIGS. 2C-2D, may provide input signalsto processor 410. The input signals may be indicative of the respiratorybehavior or other functions of the patient and may be used to detect thepresence and/or absence of disturbed breathing, for example, asdescribed above with respect to FIGS. 2A-2D.

The processor 410 may receive one or more input signals from sensors240, or sensors located elsewhere, and in response thereto may providesignals and/or drive signals (DRV) to a number of the electrodes210(1)-210(n). As described above, the signals and/or drive signals(e.g., voltage and/or current waveforms) generated by waveform generator411 may cause one or more of the electrodes 210(1)-210(n) toelectrically stimulate one or more portions of the patient's oral cavityOC in a manner that shortens the patient's Palatoglossus muscle PGM.Shortening the Palatoglossus muscle PGM in response to electricalstimulation provided by one or more of the electrodes 210(1)-210(n) may(1) stiffen and reduce the volume of the tongue T, (2) may cause thetongue to cinch downward, and (3) may cause the Palatoglossal arch PGAto pull down (e.g., in a downward direction) towards the base of thetongue T. In this manner, the electrical stimulation provided by the oneor more electrodes 210(1)-210(n) may prevent the tongue T fromprolapsing onto the back of the pharynx PHR and/or may prevent the softpalate SP from collapsing onto the back of the pharynx PHR and/or mayprevent the tissues from vibrating.

As mentioned above, the waveforms generated by the waveform generator411, when provided as signals and/or drive signals to the electrodes210(1)-210(n), primarily induce a current across the patient's upperairway in a manner that causes the patient's Palatoglossus muscle PGM toshorten. The waveforms generated by the waveform generator 411 mayinclude continuous (analog) voltage waveforms, any number of pulses thatmay vary in shape and duration as a pulse train, or the pulses may becombined to simulate an analog waveform or a combination of both, andmay be dynamically modified by the waveform generator 411. In otherimplementations, the waveforms generated by the waveform generator 411may be digital pulses.

The optional transceiver 420 may be used to transmit control information(CTL) and/or data, and/or receive control information and/or data froman external device via a suitable wired or wireless connection. Theexternal device (not shown for simplicity) may be any suitable displaydevice, storage device, distribution system, transmission system, andthe like. For one example, the external device may be a display (e.g.,to display the patient's respiratory behavior or patterns, to alert anobserver to periods of electrical stimulation, to indicate an alarm ifbreathing stops, and so on).

For another example, the external device may be a storage device thatstores any data produced by appliance 200, perhaps including thepatient's respiratory behavior, the electrical stimulation provided byappliance 200, the waveforms provided by waveform generator 411, and/orrelationships between two or more of the above. More specifically, forsome embodiments, the external device may store data for a plurality ofpatients indicating, for example, a relationship between the applicationof electrical stimulation to the patient and the patient's respiratoryresponse to such electrical stimulation, and may include otherinformation. Such relationship data for large numbers of patients may beaggregated, and thereafter used to identify trends or common componentsof OSA across various population demographics. The storage device may bea local storage device, or may be a remote storage device (e.g.,accessible via one or more means and/or networks including but notlimited to such as a wide area network (WAN), a wireless local areanetwork (WLAN), a virtual private network (VPN), and/or the Internet).The data and information may be made available and/or manipulatedlocally and/or remotely, and may be utilized immediately and/orpreserved for later utilization and/or manipulation.

Memory 412 may include a non-transitory computer-readable storage medium(e.g., one or more nonvolatile memory elements, such as EPROM, EEPROM,Flash memory, a hard drive, etc.) that may store the following softwaremodules and/or information:

a function select module to selectively switch an active function of theelectrodes 210 between an electrode mode (e.g., provided by one or moreof electrodes 210 and a sensor mode (e.g., provided by one or more ofsensors 240);

a control module to selectively provide signals and/or drive signals tothe electrodes 210, for example, to induce an electric current across aportion of the patient's oral cavity in accordance with the presentembodiments and/or to receive input signals from the sensors 240; and

a data collection module to record data indicative of the patient'srespiratory or other behavior and/or to transmit such data to anexternal device.

Each software module may include instructions that, when executed by theprocessor 410, may cause appliance 400 to perform the correspondingfunction. Thus, the non-transitory computer-readable storage medium ofmemory 412 may include instructions for performing all or a portion ofthe operations described below with respect to FIG. 6. The processor 410may be any suitable processor capable of executing scripts ofinstructions of one or more software programs stored in the appliance400 (e.g., within memory 412). For at least some embodiments, memory 412may include or be associated with a suitable volatile memory, forexample, to store data corresponding to the patient's respiratoryfunctions and/or corresponding to the electrical stimulation provided bythe appliance 200.

As mentioned above, the control circuit 220 may control the duration ofpulses that induce the current 201 across the patient's oral cavity, forexample, to minimize carrier depletion within the patient's lingualtissues and/or may from time to time reverse the direction of theinduced current 201, for example, to provide a zero sum drive waveform(e.g., to minimize or preclude electrochemical activity and/or tominimize the patient's awareness of any electrical activity related tooral appliance 200). For at least one embodiment, the control circuit220 may select the pulse lengths (and/or other characteristics of thewaveforms) based upon a resistive-capacitive (RC) time constant model ofthe patient's tongue T. For example, FIG. 5 shows an RC time constantmodel 500 of the patient's tongue T. The model 500 is shown to include acapacitor C and two resistors, R1 and R2. For an example embodiment, thecapacitor C may be approximately 0.5 uF, the resistor R1 may beapproximately 600 ohms, and the resistor R2 may be approximately 4,000ohms. Thus, for the example embodiment, the time constant τ=R1*C may bea value approximately equal to 300 μs. The resistor R2 represents minor“DC current” flow in the model, where the current stabilizes at a smallbut non-zero value after more than 5 time constants or when DC isapplied to the electrodes.

More specifically, Applicant has discovered that a typical patient'stongue T is often most receptive to a current “pulse duration” that isequal to or shorter than a time period approximately equal to τ=R1*C≈300μs. After the time period 3τ≈1 ms expires, the patient's tongue T mayexhibit an even greater increase in impedance, or perhaps experience iondepletion, which in turn requires greater voltage levels to continueinducing the current 201 across the patient's upper airway tissues. Asnoted above, increasing the voltage levels to continue inducing thecurrent 201 across the patient's upper airway tissues may not only wastebattery or wired power but also may cause discomfort (or even pain) tothe patient. Indeed, because current regulators typically utilize theiravailable voltage “headroom” to increase the drive voltage and maintaina constant current flow when the load impedance increases or when theeffective drive voltage otherwise decreases, it is important todynamically manage the effective drive voltage provided by theelectrodes 210(1)-210(2).

The effective drive voltage may decrease when there is an increasedimpedance, or perhaps ion depletion, in the patient's tongue, and thedrive resistance may increase when one (or both) of the electrodes210(1)-210(2) loses contact with the patient's sublingual tissues,generally causing the control circuit 220 to increase its drive voltagein an attempt to maintain a prescribed current flow. Thus, for at leastsome embodiments, the control circuit 220 may be configured to limit thedrive voltage and/or the current to levels that are known to be safe andcomfortable for the patient, even if the drive impedance becomesunusually high. In addition, the control circuit 220 may be configuredto from time to time reverse the polarity or direction of the inducedcurrent 201. The reversal of the current 201 can be performed at anytime. The timing of the reversal of current 201 may be selected suchthat there is no net transfer of charge across the patient's sublingualtissues (e.g., a zero sum waveform).

FIG. 6 is a flow chart 600 depicting an example operation for providingelectrical stimulation to a patient in accordance with the presentembodiments. Although the flow chart 600 is discussed below with respectto appliance 200 of FIGS. 2A-2B, the flow chart 600 is equallyapplicable to other embodiments discussed herein. Prior to operation,the appliance 200 is positioned within a sublingual portion of thepatient's oral cavity, for example, so that the electrodes 210(1)-210(2)are positioned on opposite sides of the patient's tongue proximate tothe lateral posterior regions (e.g., points) 101 at which thePalatoglossus muscle PGM inserts into the tongue T (see also FIGS.1A-1B). Once the appliance 200 is properly fitted within the patient'soral cavity, the appliance 200 accepts zero or more input signals usinga number of sensing circuits provided on or otherwise associated withappliance 200 (601). As discussed above, the input signals may beindicative of the respiratory state or other behavior of the patient,and may be derived from or generated by any suitable sensor. The controlcircuit 220 generates a number of control and/or drive signals based onthe input signals. (602).

In response to the signals and/or drive signals, the electrodes210(1)-210(2) induce a current in a lateral direction across asublingual portion of the patient's tongue (603). The current inducedacross the sublingual portion of the patient's tongue electricallystimulates the patient's Palatoglossus muscle (604). As described above,electrically stimulating the patient's Palatoglossus muscle may shortenthe Palatoglossus muscle (604A), may pull down the patient's soft palatetowards the base of the tongue (604B), may decrease the volume of thetongue (604C), and/or may prevent anterior movement of the tongue(604D).

For some embodiments, the induced current may be a reversible current.For at least one embodiment, the reversible current may be a zero-sumwaveform. For such embodiments, the control circuit 220 may from time totime reverse a polarity of the reversible current (605), and/or mayadjust the duration and/or amplitude of voltage and/or current pulsesand/or waveforms based on the RC time constant model of the patient'stongue (606).

FIGS. 7A-7D show a removable oral appliance 700 in accordance with otherembodiments. The oral appliance 700, which may be used to treat OSA(and/or other types of disordered breathing, discussed in more detailbelow with respect to FIGS. 8A-8B, 9A-9F, and 10A-10F) by providingelectrical stimulation to a patient's sublingual tissues in a mannerthat causes the Palatoglossus muscle to shorten, is shown to include anappliance body 705 (which includes portions 705(1)-705(3), as shown inthe FIGS.) upon which electrodes 210(1)-210(2), control circuit 220, andpower supply 230 may be mounted (or otherwise attached to) so as to forma unitary and removable device that may fit entirely within a patient'soral cavity OC (see also FIGS. 1A-1B). The oral appliance 700, which mayoperate in a similar manner as the oral appliance 200 of FIGS. 2A-2B,includes appliance body 705 instead of appliance body 205 of FIGS.2A-2B. Specifically, appliance body 705 includes two anchor portions705(1)-705(2) and a support wire 705(3). The anchor portions705(1)-705(2) may be fitted over opposite or approximately oppositemolars of the patient, with the support wire 705(3) connected betweenanchor portions 705(1)-705(2) and extending along the patient's gumline. For other embodiments, the appliance body 705 may be attached,inserted, or otherwise positioned within the patient's oral cavity inany technically feasible manner.

More specifically, for the example embodiments described herein, thefirst electrode 210(1) may be attached to or otherwise associated withthe first anchor portion 705(1), and the second electrode 210(2) may beattached to or otherwise associated with the second anchor portion705(2). For other embodiments, one or both of the anchor portions705(1)-705(2) may be omitted (e.g., the appliance body 705 may be a“floating” system in which the electrodes 210(1)-210(2) are positionedwithin the patient's oral cavity without anchors that fit over thepatient's teeth. The control circuit 220 may be attached to support wire705(3) and/or the second anchor portion 705(2), and the power supply 230may be attached to support wire 705(3) and/or the first anchor portion705(1) and/or the second anchor portion 705(2). Wires 221 (not shown inFIGS. 7A-7D for simplicity) may be attached to or provided within thesupport wire 705(3).

In the foregoing specification, the example embodiments have beendescribed with reference to specific example embodiments thereof. Itwill, however, be evident that various modifications and changes may bemade thereto without departing from the broader scope of the disclosureas set forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is:
 1. A method for treating apnea in a patient, themethod comprising: generating one or more signals indicative of thepatient's respiratory behavior; and electrically stimulating at least aportion of the patient's upper airway based on the one or more signals,the electrical stimulation configured to target the patient'sPalatoglossus muscle.
 2. The method of claim 1, wherein the electricalstimulation is configured to avoid the patient's Hypoglossal nerve. 3.The method of claim 1, wherein the electrical stimulation is configuredto pull the patient's Palatoglossal arch in a downward direction towardsa base of the patient's tongue.
 4. The method of claim 1, wherein theelectrical stimulation is configured to decrease a volume of thepatient's tongue.
 5. The method of claim 1, wherein the electricalstimulation is configured to shorten the patient's Palatoglossus muscle.6. The method of claim 1, wherein the electrical stimulation isconfigured to elevate a posterior region of the patient's tongue withoutmoving the patient's tongue in an anterior direction.
 7. The method ofclaim 1, further comprising: dynamically adjusting the electricalstimulation based, at least in part, on the one or more signals.
 8. Themethod of claim 1, further comprising: indicating a presence ofdisturbed breathing based on the one or more signals.
 9. The method ofclaim 1, wherein the electrically stimulating comprises: inducing acurrent configured to flow in a lateral direction across at least aportion of the patient's tongue.
 10. The method of claim 9, wherein theinduced current comprises a reversible current.
 11. The method of claim10, wherein the reversible current comprises a zero-sum waveform. 12.The method of claim 9, further comprising: periodically reversing apolarity of the induced current.
 13. The method of claim 9, wherein apulse length of the induced current is configured according to aresistive-capacitive (RC) time constant model associated with thepatient's tongue.
 14. The method of claim 1, wherein the electricalstimulation is provided by a number of electrodes configured to be inphysical contact with lateral points at which the Palatoglossus muscleinserts into the patient's tongue.
 15. The method of claim 1, furthercomprising: correlating the electrical stimulation with an immediaterespiratory response of the patient.
 16. The method of claim 1, whereinthe one or more signals comprise electromyogram (EMG) signals.
 17. Anon-transitory computer-readable storage medium storing one or moreprograms containing instructions that, when executed by one or moreprocessors of a device, cause the device to treat apnea in a patient byperforming operations comprising: generating one or more signalsindicative of the patient's respiratory behavior; and electricallystimulating at least a portion of the patient's upper airway based onthe one or more signals, the electrical stimulation configured to targetthe patient's Palatoglossus muscle.
 18. The non-transitorycomputer-readable storage medium of claim 17, wherein the electricalstimulation is configured to avoid the patient's Hypoglossal nerve. 19.The non-transitory computer-readable storage medium of claim 17, whereinthe electrical stimulation is configured to pull the patient'sPalatoglossal arch in a downward direction towards a base of thepatient's tongue.
 20. The non-transitory computer-readable storagemedium of claim 17, wherein the electrical stimulation is configured todecrease a volume of the patient's tongue.
 21. The non-transitorycomputer-readable storage medium of claim 17, wherein the electricalstimulation is configured to shorten the patient's Palatoglossus muscle.22. The non-transitory computer-readable storage medium of claim 17,wherein the electrical stimulation is configured to elevate a posteriorregion of the patient's tongue without moving the patient's tongue in ananterior direction.
 23. The non-transitory computer-readable storagemedium of claim 17, wherein execution of the instructions causes thedevice to perform operations further comprising: dynamically adjustingthe electrical stimulation based, at least in part, on the one or moresignals.
 24. The non-transitory computer-readable storage medium ofclaim 17, wherein execution of the instructions causes the device toperform operations further comprising: indicating a presence ofdisturbed breathing based on the one or more signals.
 25. Thenon-transitory computer-readable storage medium of claim 17, whereinexecution of the instructions for electrically stimulating causes thedevice to perform operations further comprising: inducing a currentconfigured to flow in a lateral direction across at least a portion ofthe patient's tongue.
 26. The non-transitory computer-readable storagemedium of claim 25, wherein the induced current comprises a reversiblecurrent.
 27. The non-transitory computer-readable storage medium ofclaim 26, wherein the reversible current comprises a zero-sum waveform.28. The non-transitory computer-readable storage medium of claim 25,wherein execution of the instructions causes the device to performoperations further comprising: periodically reversing a polarity of theinduced current.
 29. The non-transitory computer-readable storage mediumof claim 25, wherein a pulse length of the induced current is configuredaccording to a resistive-capacitive (RC) time constant model associatedwith the patient's tongue.
 30. The non-transitory computer-readablestorage medium of claim 17, wherein execution of the instructions causesthe device to perform operations further comprising: correlating theelectrical stimulation with an immediate respiratory response of thepatient.
 31. The non-transitory computer-readable storage medium ofclaim 17, wherein the one or more signals comprise electromyogram (EMG)signals.